1. Field of the Invention
The present invention relates to an optical lens assembly, and especially to an optical lens assembly having a fluorescent layer for preventing the moisture from entering the fluorescent layer formed therein, and thereby the optical performance of the fluorescent layer can be maintained over a long period, and thus the optical lens assembly of the present invention can be applied to the array-type LED packaging.
2. The Prior Arts
An LED is a semiconductor light source, which operates based on the recombination of carriers (electrons and holes) in a semiconductor. When an electron carrier in the conduction band combines with a hole in the valence band, it loses energy equal to the bandgap in the form of an emitted photon; i.e., light. The LEDs have the advantages of compact size, fast start-up time, and high efficiency so that they can be applied to various applications especially in the field of solid-state lighting.
Referring to FIG. 1, which is a cross-sectional view showing a conventional LED package structure, which includes a substrate 10a, a package module 12a, a lead frame 14a, and an encapsulation layer 16a. The substrate 10a is installed at the bottom of the package structure. The package module 12a is served to integrate the substrate 10a and the lead frame 14a. The LED chips 18a are arranged on the substrate 10a in an array form, and the substrate 10a is made of a metal material. The LED chips 18a are electrically connected to the lead frame 14a. The encapsulation layer 16a is tightly connected to the package module 12a. An insulating protective layer 20a is formed on the LED chips 18a for covering the LED chips 18a. Then, a fluorescent layer 22a is formed on the insulating protective layer 20a. 
However, one disadvantage of the prior art is that the fluorescent layer formed above the LED chips is directly in contact with moisture in the air. It is known that a fluorescent material can absorb moisture from the air, and would result in the deterioration in light emission properties, and the level of white light would gradually decay. Moreover, the fluorescent layer can directly absorb heat generated by light irradiation. In general, the heat resistant temperature and thermal stability of a fluorescent layer are relatively low, and thereby once heat generated by light irradiation is conducted to the fluorescent layer, the fluorescent material would deteriorate over time, and consequently the illumination efficiency is decreased and the chromaticity is altered.
Moreover, if a fluorescent material is formed on an LED chip by filling or coating method, an extra amount of the fluorescent material has to be provided for ensuring that the fluorescent material will be substantially uniform on the LED chip, which will increase the manufacturing cost. Furthermore, if the fluorescent layer has flaws, the LED chip can not be reused. Conventionally, various optical tests can only be carried out after the formation of the fluorescent layer. Therefore, there is a need to provide an LED package structure which can be optically tested in advance, has relatively low manufacturing cost, and has excellent optical mixing and heat dissipation properties.